Plate filter element for an air filter

ABSTRACT

The invention relates to a plate filter element for an air filter comprising a zigzag-shaped, folded strip material made of an activated carbon nonwoven material. The aim of the invention is to improve the dimensional stability of the activated carbon nonwoven material, especially in the area of an end fold. To this end, the invention provides that an end fold of the strip material comprises a sealing which is formed by gluing or fusing an upper side with an underside of the activated carbon nonwoven material.

CROSS REFERENCE TO RELATED APPLICATIONS

Applicants claim priority under 35 U.S.C. §119 of German Application No.198 44 874.0 filed Sep. 30, 1998. Applicants claim priority under 35U.S.C. §120 of PCT/DE99/03016 filed Sep. 17, 1999. The internationalapplication under PCT article 21(2) was not published in English.

The invention relates to a plate filter element for an air filter,having a zigzag-folded web material made of an active carbon nonwoven,which has an upper side of nonwoven material and an underside ofnonwoven material and active carbon particles arranged between them.

DE 195 24 677 Al discloses a plate filter element which has azigzag-folded web material. In this filter element, an end fold of theweb material is adhesively bonded with a fold adjacent to it. In thiscase, the mutually opposite sides of the adjacent folds are bonded toone another by means of an adhesive bond in order to achieve sealing ofthe web material.

Other known plate filter elements have a zigzag folded web materialwhich is formed from an active carbon nonwoven. Such an active carbonnonwoven has at least an upper side made of nonwoven material and anunderside made of nonwoven material, active carbon particles beingarranged between the upper side and underside. The active carbonparticles can in this case adhere by means of an adhesive to themutually facing inner sides of the upper side of the nonwoven and theunderside of the nonwoven. This layer construction forms a deformablenonwoven composite, the active carbon particles being held relativelyloosely between the nonwoven layers, so that active carbon particles canbe detached from the nonwoven composite, in particular at the edgeregions of the active carbon nonwoven.

Fixed to the side edges of the web material, running transversely withrespect to the folds, are side bands or side strips which, inter alia,are used to impart dimensional stability to the zigzag-folded activecarbon nonwoven. As a result of these side strips, enclosing the foldedactive carbon nonwoven at the sides, it is additionally possible foractive carbon particles to be prevented from emerging laterally from thecomposite. The side strips are additionally regularly intended toperform a sealing function.

However, at the end folds of the folded active carbon nonwoven, activecarbon particles can continue to emerge from the nonwoven composite. Inaddition, the nonwoven composite can be damaged relatively easily at theend folds, in particular it may split open. This means that the nonwovenlayers can become detached from one another. As a result, theintroduction of an active carbon nonwoven damaged in this way into anenclosure provided for the end fold, even in a specific frame of theplate filter element or directly in a filter housing, is made moredifficult. The end fold of the web material is additionally subjected toa relatively high bending stress as a result of its attachment to theside strips, and this stress, in particular in the center between theside strips, has the effect of bulging out this end fold in thelongitudinal direction of the side strips. This stress promotes orsupports the splitting open or separation of the layers of the activecarbon nonwoven composite.

The present invention tackles the problem of improving the dimensionalstability of the active carbon nonwoven in a plate filter element of thetype mentioned at the beginning.

According to the invention, this problem is solved by a plate filterelement having the features of the claims.

The invention is based on the general idea at the exposed end edge ofthe web material, of joining the upper side of the active carbon filterto the underside of the active carbon nonwoven in a sealed manner, sothat firstly it is made more difficult for the active carbon nonwovencomposite to split open or for the upper layer to become detached fromthe under layer and, secondly, the emergence of active carbon particlesfrom the active carbon nonwoven in the area of the end fold isprevented. In order to achieve this, the invention proposes to providethe end fold or its end edge with a seal. Such a seal is in this caseachieved by an adhesive bond or by a weld between the upper side and theunderside of the active carbon nonwoven.

The adhesive bond for forming the seal is preferably formed with the aidof an adhesive which, for this purpose, penetrates at least partiallythrough the elements to be bonded to one another and embeds them.Alternatively, the bond can also be achieved by one of the elements tobe adhesively bonded to each other to be more or less liquefied bymelting, the liquefied element penetrating into a non-liquefied elementand penetrating at least partially through the latter and embedding itin the melt.

A weld for forming the seal can be achieved, for example, by theelements to be welded to each other being liquefied by melting and, inthe process, fusing to one another.

In order to increase the dimensional stability of the end fold further,a development of the invention proposes compressing the web material inthe area of the seal. In this way, the strength of the connection formedbetween the elements connected to one another is increased.

In addition, a process is proposed for the production of the platefilter element according to the invention. According to the process forthe production of a plate filter element according to the inventionultrasonic welding is preferred, the ultrasonic “welding” here includingboth welding in which the two elements to be joined to each other aremore or less liquefied and thus fuse to each other or melt together witheach other, and also an adhesive bonding in which one of two elements tobe joined to each other is more or less liquefied and penetrates atleast partially through the non-liquefied element and embeds it in themelt formed.

According to a preferred embodiment of the process according to theinvention, firstly an end band which is equipped with a hot-meltadhesive layer is applied to the area of the web material provided forthe end fold. The ultrasonic welding operation which follows willliquefy this hot-melt adhesive layer, so that the liquid hot-meltadhesive penetrates through both the end band formed from a nonwovenmaterial and the nonwoven on the upper side and the nonwoven on theunderside of the active carbon nonwoven, as well as active carbonparticles arranged between the latter, these elements to be joined toone another being embedded in the hot-melt adhesive. In this way,efficient sealing with a high dimensionally stabilizing effect isachieved. This process can preferably be improved by the components tobe joined to one another, such as the end band nonwoven and the activecarbon nonwoven, being compressed during the ultrasonic weldingoperation.

Further important features and advantages of the plate filter elementaccording to the invention emerge from the subclaims, from the drawingsand from the associated figure description referring to the drawings.

A preferred exemplary embodiment of the invention is illustrated in thedrawings and will be explained in more detail in the followingdescription. In the drawings, in each case in schematic form,

FIG. 1 shows a plan view of a plate filter element according to theinvention, and

FIG. 2 shows a sectioned side view corresponding to the section lines IIin FIG. 1 on an enlarged scale.

According to FIG. 1, a plate filter element 1 according to the inventionhas a zigzag-folded web material made of an active carbon nonwoven 2.Transversely with respect to the folds of the active carbon nonwoven 2the plate filter element 1 is enclosed laterally by side strips or sidebands 3. The side bands 3 are preferably composed of a nonwoven materialand are welded or adhesively bonded to the ends of the folds. By fixingthe side bands 3 to the folds of the active carbon nonwoven 2,dimensional stability can be insured for the zigzag form of the foldedactive carbon nonwoven 2. In addition, the side bands 3 form a seal.

Fixed to an end fold 4, illustrated on the left in FIGS. 1 and 2, is anend band 5. The end band 5 has approximately the same height 6 as theend fold 4. However, the attachment of the end band 5 to the end fold 4is not carried out over the entire height 6, but only in a subarea 7,which is identified by a curly bracket in FIG. 2 and extendsapproximately over the lower half of the height 6.

According to FIG. 2, the end band 5 is fitted to the outer side of theend fold 4, facing away from the remaining folds of the active carbonnonwoven 2. Also possible is an embodiment in which the end band 5 isfixed to the inner side of the end fold 4, facing the remaining folds ofthe active carbon nonwoven 2.

In the subarea 7 in which the attachment of the end band 5 to the endfold 4 is formed, the thickness of the end fold 4 and that of the endband 5 are reduced with respect to the areas located outside the subarea7. This thickness reduction is based on compression of the material,which is carried out during the formation of the attachment of the endband 5 to the end fold 4.

In order to impart increased dimensional stability to the free end ofthe end fold 4, and to reduce the emergence of active carbon particles12 from the active carbon nonwoven 2, the end fold 4 is sealed in thesubarea 7. In the preferred embodiment illustrated in FIG. 2, this sealis formed by adhesively bonding an upper-side nonwoven 10 to anunderside nonwoven 11 of the active carbon nonwoven 2 by means of anadhesive. For this purpose, the end band 5 bears a hot-melt adhesivelayer 8.

In order to form the seal, the end band 5 is placed onto the end fold 4in such a way that the hot-melt adhesive layer 8 comes to rest on theend fold 4. The elements lying on each other (end band 5 with hot-meltadhesive layer 8, endfold 4) are introduced between a sonotrode and anangle of an ultrasonic welding device and subjected to an ultrasonicwelding operation. At the same time, increased pressure is additionallyexerted on the elements to be joined to one another, so that thecompression mentioned further above takes place.

As a result of the ultrasonic welding operation, in a preferredembodiment, only the hot-weld adhesive layer 8 is more or lessliquefied. If appropriate, a hot-melt adhesive in the active carbonnonwoven can also be liquefied, and used there to stick the activecarbon particles together. The liquefied hot-melt adhesive penetratesinto the nonwoven materials, that is to say into the end band 5,preferably formed from a nonwoven, and into the nonwoven layers of theactive carbon nonwoven 2, or at least partially penetrates through thesenonwoven materials. Furthermore, the liquid hot-melt adhesive penetratesthrough the active carbon particles 12 arranged in the active carbonnonwoven between the upper side 10 and the underside 11 of the activecarbon nonwoven 2. The non-liquefied components are therefore embeddedin the melt of the hot-melt adhesive. As soon as the hot-melt adhesivecools down, a high-strength composite is formed, by means of which,firstly, the free end of the end fold 4 is sealed and by means of which,secondly, the end band 5 is attached to the end fold 4.

A section 9 of the end band 5 which adjoins the subarea 7 attached tothe end fold 4 can serve as a seal which seals off the plate filterelement 1 with respect to a frame part (not illustrated) of the platefilter element 1 into which the end fold 4 is introduced, or withrespect to a filter housing (likewise not illustrated) into which thefilter element 1—then without the aforementioned frame part—isintroduced. If the end band 5 in the section 9 is to have such a sealingfunction, it is preferably produced from a nonwoven material.

If such a sealing function is not required of an end band 5, it is notnecessary either for the end band 5 to extend over the entire height 6of the end fold 4. Moreover, the end band 5 itself can also be formed asa hot-melt adhesive. Also possible is a design in which the end band 5consists of a fusible nonwoven, which is liquefied by the ultrasonicwelding and penetrates into the active carbon nonwoven or penetratesthrough the latter and embeds the non-molten or non-liquefied componentsin the melt. In this case, a special hot-melt adhesive layer on the endband 5 can be dispensed with.

What is claimed is:
 1. A plate filter element for an air filter, havinga zigzag-folded web material made of an active carbon nonwoven, whichhas an upper side of nonwoven material and an underside of nonwovenmaterial and active carbon particles arranged between them, a free endof an end fold (4) of the web material having a seal which is formed byadhesively bonding or by welding the upper side (10) to the underside(11) of the active carbon nonwoven (2).
 2. The plate filter element asclaimed in claim 1, characterized in that the adhesive bond is formedwith an adhesive (8) or by fusing at least one of the elements to beadhesively bonded to each other.
 3. The plate filter element as claimedin claim 2, characterized in that a molten element penetrates into anon-molten element (4, 5, 12) of the elements (4, 5, 12) to be bonded toeach another, or penetrates at least partially through the latter andembeds it in the melt.
 4. The plate filter element as claimed in claim1, characterized in that the weld is formed by fusing the elements to bewelded to each other.
 5. The plate filter element as claimed in claim 1,characterized in that the web material is compressed in the area (7) ofthe seal.
 6. The plate filter element as claimed in claim 1,characterized in that the end fold (4) is provided with an end band (5)which is fixed to the end fold (4) by the adhesive bonding or by thewelding.
 7. The plate filter element as claimed in claim 6,characterized in that the end band (5) has approximately the same height(6) as the end fold (4), and in that the adhesive bond or weld extendsover only part (7) of the height (6) of the end fold (4), the end band(5) outside the adhesive bond or weld serving as a seal (9).
 8. Theplate filter element as claimed in claim 6, characterized in that theend band (5) consists of a nonwoven material.
 9. The plate filterelement as claimed in claim 2, characterized in that the adhesive (8) isa hot-melt adhesive.
 10. The plate filter element as claimed in claim 1,characterized in that the web material, transversely with respect to itsfolds, is enclosed between two side webs (3) which are formed of anonwoven material and which are fixed to the web material by adhesivebonding or by welding, and in that the end band (5) is fixed to the sidewebs (3).
 11. A process for producing a plate filter as claimed in claim1, characterized in that the seal is formed, in an area of the webmaterial provided for the end fold (4), by means of an ultrasonicwelding operation in which at least one component (8) of the elements(4, 5, 8, 12) to be joined to one another is more or less liquefied,liquefied components (8) fusing to one another or melting together withone another and non-liquefied components (4, 5, 12) being penetratedthrough, at least partially, by the at least one liquefied component (8)and embedded in the latter.
 12. The process as claimed in claim 11,characterized in that the ultrasonic welding operation liquefies ahot-melt adhesive contained in the active carbon nonwoven (2).
 13. Theprocess as claimed in claim 11, characterized in that the ultrasonicwelding operation liquefies a hot-melt adhesive layer (8) applied to theend fold (4).
 14. The process as claimed in claim 13, characterized inthat the hot-melt adhesive layer (8) is applied to an end band (5)attached to the end fold.
 15. The process as claimed in claim 11,characterized in that the ultrasonic welding operation more or lessliquefies a nonwoven material (10, 11) contained in the active carbonnonwoven (2).
 16. The process as claimed in claim 11, characterized inthat the ultrasonic welding operation more or less liquefies an end band(5) which is applied to the end fold (4) and consists of a nonwovenmaterial.
 17. The process as claimed in claim 11, characterized in thatduring the ultrasonic welding operation, the elements (4, 5, 8, 12) tobe joined to one another are compressed.